Modelling childhood survival with serious congenital heart defects

Abstract

Congenital heart defects (CHDs) are the most prevalent type of congenital
anomaly and the principal cause of death from congenital anomalies during
infancy. However reliable information about longer-term survival and the
factors predictive of death during later childhood is lacking.
In this thesis, I report the findings of a multicentre cohort study established to
estimate survival with serious CHDs from birth to 15 years of age and to
investigate the independent effects of early life and procedure-related factors
on mortality risk. The hospital records of 3,897 children (57% boys) born in the
UK between 1992 and 1995 and who required intervention or died in the first
year of life were reviewed. Multiple imputation of missing data including time
varying covariates was performed using multilevel statistical techniques.
Survival was estimated using Kaplan-Meier, Cox proportional hazards and
multilevel models and predictive factors evaluated using step-wise logistic
regression models using complete case as well as multiple imputed datasets.
By 15 years of age, 932 children had died, 144 without any procedure. Overall,
survival to one year was 79.8% (95% Confidence Intervals [CI] 78.5, 81.1%) and
to 15 years was 71.7% (63.9, 73.4%), with variation by cardiac diagnosis. In the
multilevel imputed data model including children who had at least one
procedure, higher mortality risk was independently associated with multiple cardiac malformations, younger age at first procedure, lower weight and/or
height, longer duration of cardiopulmonary bypass and circulatory arrest, and
presence of pre- or post-procedure complications.
Although the risk of death from CHDs is highest in the first year, an important
continuing risk of death remains throughout childhood. Early life and
procedure-related factors predict mortality risk independently of CHD
diagnosis. Future research should address social, educational, and health
outcomes in later childhood to understand the impact of advances in diagnosis
and management of CHDs.